1. Field of the Invention
The present invention relates to a coaxial counter-rotating unmanned helicopter in which upper and lower main rotors rotating in opposite directions to each other are provided on a main mast and which flies by a remote control or an autonomous control.
2. Description of Related Art
A coaxial counter-rotating helicopter is configured to simultaneously achieve a generation of lift and an offset of torque by rotating upper and lower main rotors disposed coaxially along the main mast in opposite directions to each other, and a direction control (a control of a yaw axis) of a nose of an aircraft changed to a tail rotor is achieved by providing a difference in pitch angles of the rotor blades in the upper main rotor and the lower main rotor in a variable pitch type.
In this case, in a configuration in which the tilting of the upper and lower main rotors are individually controlled by a method, such as attaching a servo to the main mast, to provide a difference in the pitch angles of the upper and lower rotor blades, mechanisms around the main mast become significantly complicated (for example, see Patent Document 1).
Therefore, a configuration has been known in which an inner shaft is provided inside a main mast in a vertically movable manner, a relay link device connected via an upper swash plate, a rod, and a link arm is disposed in a portion between an upper main rotor of the main mast and the upper swash plate, a connecting rod provided vertically downward through a yoke of the upper main rotor from a leading end of the inner shaft is connected to the relay link device, the inner shaft is vertically moved to vertically displace the relay link device, as a result, a fixed arm of the upper main rotor connected to the upper swash plate via the rod is rotationally moved to change a pitch angle of a rotor blade, and thus, a control of a yaw axis of an aircraft is performed (for example, see Patent Document 2).